1. International Laboratory for Quantum Functional Materials of Henan and School of Physics and Engineering, Zhengzhou University, Zhengzhou 450001, China
2. Department of Chemistry and London Centre for Nanotechnology, University College London, London WC1H, United Kingdom
3. ICQD, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China
4. Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
5. Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA
6. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA